In order to control the Exhaust Gas Recirculation (EGR), the control module operates the linear EGR valve. The linear EGR valve is a small motor with a pintle that is normally closed. By providing a ground path, the control module will open the pintle and allow the exhaust gasses to pass through the valve. The control module of the EGR is based on the following inputs:
• | The engine coolant temperature - above 25°C. |
• | The TP OFF idle |
• | MAP |
• | BARO |
• | Park/Neutral position |
• | The pintle position sensor. |
If DTC P0401 or P1406 is stored, refer to the applicable DTC table. This chart is used for a malfunctioning valve, plugged EGR passages, or improper wiring connections.
The numbers below refer to the step numbers in the diagnostic table.
At idle, the EGR valve should not be open greater than 3 %. A faulty park/neutral position Trans Range (TR) position pressure switch or the EGR valve stuck open will allow exhaust gasses to enter the combustion chamber and create a rough idle condition.
This step checks the ability of the pintle to be manually commanded to the desired positions.
This step checks the electrical circuit of the EGR valve and connecting components.
This step checks for plugged EGR passages or a faulty EGR valve.
Step | Action | Value(s) | Yes | No |
---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Is the actual EGR pintle position greater than the specified value? | 0 % 2000 RPM 3 % | |||
Is the actual EGR pintle position stable, and within 10 % of position of desired EGR pintle position command after the specified value? | 3 sec 2 sec | |||
4 | Set the EGR pintle position to the specified value. Did the MAP increase when the actual pintle responded? | 25 % | ||
5 | Set desired EGR pintle position to specified value. Is the desired EGR pintle position at the specified value? | 100 % | -- | |
6 |
Is the action complete? | -- | ||
7 |
Is the action complete? | -- | ||
8 |
Is the action complete? | -- | ||
9 |
Is the voltage at the specified value? | 5 V | ||
10 |
Hold in the pintle of EGR valve. Is any voltage present? | -- | ||
Is the action complete? | -- | |||
12 | Replace the control module. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |
Is the action complete? | -- | -- | ||
14 | Replace the EGR valve. Refer to EGR Valve Replacement for the 4.3L, 5.0L, 5.7L. Refer to Exhaust Gas Recirculation Valve Replacement for the 7.4L. Is the action complete? | -- | -- | |
15 |
Is the action complete? | -- | -- | |
16 |
Does the component operate properly? | -- | System OK |
With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:
• | The engine stops after a cold start. |
• | The engine stops at idle after deceleration. |
• | The vehicle surges during cruise. |
• | The vehicle idles roughly.. |
If the EGR valve stays open all of the time, the engine may not idle. A DTC P0401 may set. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient for the 4.3L engine. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient for V8 applications.
Too little or no EGR flow allows the combustion temperatures to get too high during acceleration and load conditions. This could cause the following conditions:
• | Spark knock (detonation) |
• | Engine overheating |
• | DTC P0401 |
The Linear EGR System Check table covers the diagnosis of the EGR system. Refer to EGR System Diagnosis (System Check) for V6. Refer to EGR System Diagnosis (System Check) for V8.